共查询到19条相似文献,搜索用时 93 毫秒
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采用有限元固定网格和移动网格相结合的方法,求解带自由面的坝体稳定渗流问题。本方法是针对一般坝体的结构,在有限元网格生成之后,又自动生成了网格移动所需的信息,实现了网格在迭代计算中随自由面的变化自动均匀移动;讨论了网格奇异的不同类型,提出了避免单元形状怪异的移动网格方法;在欧拉空间中分区记录坝体不同的渗透性能,在网格移动到新位置后,自动识别网格所在的物性空间,从而确定单元在新位置上的渗流系数。本文将该方法应用到吉林丰满混凝土重力坝防渗加固的实际工程当中,在考虑大坝原有防渗措施的前提下,利用数值分析,研究了防渗芯墙对大坝渗流性能的影响。计算结果表明,加芯墙后坝体自由面位置明显下移,湿水部分大为减少,坝基扬压力没有明显提升,下游出水点位置没有明显下降。计算过程表明,本文方法及措施具有很好的收敛性与稳定性,且收敛性与自由面初始位置的选择无关。 相似文献
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无单元法研究和应用现状及动态 总被引:36,自引:4,他引:36
无单元法(也称无网格方法)是一种新兴的数值计算方法,它是
有限元等传统数值分析方法的重要补充和发展,极大地简化了前处理工
作与裂纹扩展等问题的计算分析.近年来,无单元法得到了迅速发展,受
到了国际计算力学界的高度重视.简要介绍了国内、外无单元法的发展
动态和应用现状,评述了无单元法的最新研究成果,归结出无单元法的
一些优点及目前尚有待解决的一些问题.最后指出了无单元法在工程应
用中将有着广阔的发展前景. 相似文献
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一种全四边形网格生成方法——改进模板法 总被引:9,自引:0,他引:9
首先对全四边形单元网格自动剖分算法中的模板法进行了探讨,并提出了相应的改进方法。在此基础上提出了一种新的全四边形单元网格自动生成方法。该方法允许在两个方向上存在网格疏密过渡,并可以提高单元的密度要求自动计算亲单元每条边上的结点数,有效地对局部实施加密处理。 相似文献
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弹性力学的一种边界无单元法 总被引:24,自引:7,他引:24
首先对移动最小二乘副近法进行了研究,针对其容易形成病态方程的缺点,提出了以带权的正交函数作为基函数的方法-改进的移动最小二乘副近法,改进的移动最小二乘逼近法比原方法计算量小,精度高,且不会形成病态方程组,然后,将弹性力学的边界积分方程方法与改进的移动最小二乘逼近法结合,提出了弹性力学的一种边界无单元法,这种边界无单元法法是边界积分方程的无网格方法,与原有的边界积分方程的无网格方法相比,该方法直接采用节点变量的真实解为基本未知量,是边界积分方程无网格方法的直接解法,更容易引入界条件,且具有更高的精度,最后给出了弹性力学的边界无单元法的数值算例,并与原有的边界积分方程的无网格方法进行了较为详细的比较和讨论。 相似文献
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针对单纯几何非线性的材料大变形问题, 提出一种新的研究思路------固定数学网
格的数值流形方法, 简称固定网格流形法, 可以看作是采用了固定网格的拉格朗日方法. 它
充分利用数值流形方法的数学网格与材料物理边界分离的特性, 具备拉格朗日法和欧拉法各
自的优势, 避免了原始拉格朗日法的网格扭曲问题以及欧拉法对移动边界难以精确
描述和迁移项较难处理的问题. 采用数值流形方法的大变形分步计算格式, 使得固定网格流形
法实现起来并不复杂, 仅需要每步切割网格形成新的流形单元, 以及对初应力载荷进行适
当的处理, 而后者是固定网格流形法的关键. 针对固定的矩形数学网格开展研究, 采用一阶
多项式覆盖函数的高阶流形法, 给出了两种初应力计算方法, 并用悬臂梁大变形算例验证了
固定网格流形法的可行性, 将来需要进一步解决初应力载荷所带来的计算稳定问题. 相似文献
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Free surface seepage analysis based on the element-free method 总被引:1,自引:0,他引:1
Element-free method (EFM) for seepage analysis with a free surface presented in the paper is based on the moving least square method which needs only the information at nodes. It avoids troublesome modifications of the mesh as in the finite element method. Being irrelative to the nodes, the mesh for quadrature is fixed throughout the iterations in determining the free surface. And the nodes can be easily added, moved or deleted in the iterations. Steady seepage and transient seepage in a uniform earth dam were analyzed in the paper. The examples show that the proposed method gives satisfactory results. 相似文献
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IntroductionSeepagefreesurfaceisoftenencounteredinthecourseofseepageproblemthroughmediaofslope,earthdamandtunnelengineering.Thephenomenaofseepagefreesurfaceisoneoftheimportantanddifficulttopicsofrockmasshydromechanics[1~3],andquiteanimportantresearch… 相似文献
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FREE BOUNDARY PROBLEM OF THE 2D SEEPAGE FLOW 总被引:2,自引:0,他引:2
FREEBOUNDARYPROBLEMOFTHE2DSEEPAGEFLOW¥SheYinghe(佘颖禾)SunYing(孙鹰)GuoXiaoming(郭小明)(DepartmentofMathematicsandMechanics,Southeast... 相似文献
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Steady free surface flows are of interest in the fields of marine and hydraulic engineering. Fitting methods are generally used to represent the free surface position with a deforming grid. Existing fitting methods tend to use time-stepping schemes, which is inefficient for steady flows. There also exists a steady iterative method, but that one needs to be implemented with a dedicated solver. Therefore a new method is proposed to efficiently simulate two-dimensional (2D) steady free surface flows, suitable for use in conjunction with black-box flow solvers. The free surface position is calculated with a quasi-Newton method, where the approximate Jacobian is constructed in a novel way by combining data from past iterations with an analytical model based on a perturbation analysis of a potential flow. The method is tested on two 2D cases: the flow over a bottom topography and the flow over a hydrofoil. For all simulations the new method converges exponentially and in few iterations. Furthermore, convergence is independent of the free surface mesh size for all tests. 相似文献
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Seepage analysis based on the unified unsaturated soil theory 总被引:2,自引:0,他引:2
The normal use of the finite element method in the analysis of earth and rock-fill dams involves troublesome modifications of the finite element mesh. In the present paper it is pointed out that in problems of steady seepage it is not necessary to determine in the iteration process the entire free surface, but only the elevation of the release point. It is shown by several examples that the proposed method can simplify the seepage analysis to a certain degree, and also give satisfactory results. 相似文献
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无单元法及其工程应用 总被引:80,自引:7,他引:80
无单元法可以求解复杂边界条件的边值问题,它只需结点信息而不需单元信息,故信息简单,特别适用于岩土工程数值分析.它的理论基础是滑动最小二乘法.本文对无单元法的基本理论作了研究,并用算例说明了研究成果. 相似文献
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The hydrodynamic problem of a cone entering the water surface obliquely has been analyzed by the three-dimensional (3-D) incompressible velocity potential theory with the fully nonlinear boundary conditions on the moving free surface and body surface boundary. The time stepping method is used in the stretched coordinate system defined as the ratio of the physical system to the distance that the cone has travelled into water. The boundary element method is used to solve the potential at each time step. Both triangular element mesh and quadrilateral element mesh have been used. Discretisation of the body surface and the free surface is applied regularly during the simulation to account for their change and deformation, and data from the old mesh is transferred into the new one through interpolation. Both the dynamic and kinematic free surface boundary conditions are satisfied through the Eulerian form. In particular the free surface elevation and potential variation are traced at a given azimuth of the cylindrical coordinate system, in the direction parallel to the body surface or perpendicular to the free surface to avoid multi-valued function. Detailed convergence study with respect to time step and element size has been undertaken and high accuracy has been achieved. Results for the cone in vertical entry are compared with those obtained from the 2-D axisymmetric method and good agreement is found. Simulations are made for cones of various deadrise angles and different oblique entries and detailed results are provided. 相似文献
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应用连续的罚函数,提出了一种改进的自由面边界条件渗流分析复合单元渗透矩阵调整法,优化了此类算法的稳定性,提高了收敛速度和精度,并将此改进算法编制成相应的有限元分析程序,应用于上海地铁4号线董家渡隧道修复基坑降水工程的优化设计,解决了基坑降水过程中复杂三维渗流场的高效精细模拟问题,同时预测了基坑中心水位降至地面以下40 m,位于承压含水层顶面以下,基坑内外自由面落差很大时基坑周边渗流场以及地面沉降的分布特征. 相似文献